What is duplicate content?

Duplicate content is a situation in which identical or nearly identical content is available at more than one URL. The search engine must then decide which version to display and ignore the others. It isn't a penalty from the rulebook, it's a consequence of the fact that the search results have room for one result, not three identical ones.

In an online store, duplicates arise in two places. Within the site, they are created by variants of the same product, filters and sorting options that generate separate URLs, and product descriptions copied from the manufacturer and used by all of its distributors. Externally, they are caused by pasting your own catalog onto a marketplace - or vice versa: launching a store using product descriptions copied verbatim from the platform where you previously sold your products.

The latter scenario is the most costly at the start, because your new product page competes with an identical page on a domain with a long-standing history. There are two solutions, and both require work: writing unique descriptions specifically for your own store, or using a canonical URL to tell the search engine which version takes precedence. The first works better; the second is faster.